Researchers use radio tags to unlock bumblebee's secrets

Saturday

Nov 30, 2013 at 12:01 AMDec 1, 2013 at 1:06 PM

WOOSTER, Ohio - Scott Prajzner leaned over the bumblebee and quickly installed a tiny radio tag by using a pair of tweezers and a spot of glue. "You have to be careful that you don't glue their wings, so they can still fly," the Ohio State University entomologist said softly as his tweezers descended to the thorax.

Spencer Hunt, The Columbus Dispatch

WOOSTER, Ohio - Scott Prajzner leaned over the bumblebee and quickly installed a tiny radio tag by using a pair of tweezers and a spot of glue.

"You have to be careful that you don't glue their wings, so they can still fly," the Ohio State University entomologist said softly as his tweezers descended to the thorax.

The insect had been knocked unconscious with a puff of carbon dioxide, so Prajzner was confident it wouldn't wake up angry.

"Every once in a while, you get a flier," he said. "But no one has been stung with our tagging research."

Prajzner estimates that he has performed the procedure 700 times. The radio tags are integral to his research to learn more about the perils bumblebees face from agricultural pesticides.

Researchers can produce reams of data on honeybees. But entomologists such as Prajzner handled bumblebees like most people who see the flying, stinging insects.

They left them alone.

Growing interest

"There are 250 species of bumblebees throughout the world, and we just don't know much about most of them," said Robbin Thorp, a University of California, Davis, professor emeritus of entomology who studies honeybees and other bee species.

Honeybees are among the most-studied insects because they're domesticated and very valuable. They annually pollinate billions of dollars' worth of fruits and vegetables in the United States.

With staggering losses of honeybees, blamed largely on a malady called colony collapse, researchers have turned their attention to other pollinating insects, including bumblebees. Their findings are both encouraging and troubling.

In California's Capay Valley near U.C. Davis, scientists found that bumblebees and other feral bee species could pollinate 100 percent of a farmer's crop. But that's if the farm was near forests where wild bees dwell.

Plus, the bumblebee's future might be just as uncertain as the honeybee's. Thorp said his concern grew the more he looked at Franklin's bumblebee, a species he started studying 15 years ago.

"The first couple of years I looked, they were everywhere they were supposed to be," he said. "Very shortly after that, they started to disappear, virtually under my view."

Similar declines were found in three other bumblebee species, including two eastern bumblebee species found in Ohio.

"Here are these four species, all closely related, and they are all declining," Thorp said.

OSU study

Prajzner's use of radio-frequency identification tags is a high-tech way to learn more about how bumblebees live in the wild.

OSU mechanical-engineering graduate student Mike Gallagher helped Prajzner design a case that contains four bee hives. Four long plastic tubes are the bees' only entry and exit points.

The tagged bumblebees trigger antennae above the tunnels that automatically update a database when the bees leave their hive on a foraging mission and again when they return.

"Some of our statistics average the amount of time bees spent out in the field and the average number of trips per hour at the hive level," Gallagher said. "And we tracked statistics for individual bees."

To study the effects of farm chemicals, Prajzner said he gave one hive a sub-lethal dose of a popular crop herbicide called 2,4 D. A second hive got a dose of a chemical that helps 2,4 D cling to plants. The third hive was treated with both compounds, while the fourth was left untouched.

Data gathered from tagged bees split among the four hives paint a stark picture of the pesticide's effects. Bumblebees from the untreated hive logged 677 trips in three weeks and spent an average of two hours away from the hive. In the herbicide-dosed hive, bumblebees took only 61 trips during the same time period and averaged five hours outside the hive.

Prajzner said the results are preliminary and must be combined with more experiments. A test set to start next summer will include a scale to record the weight of pollen each bumblebee brings to its hive to help make honey, which the bees eat. The scale is so sensitive that it can record changes in the moon's gravitational pull, Gallagher said.

The pollen data are needed to determine if the herbicide reduces bumblebees' ability to gather and build food stores for winter months, Prajzner said.

That means setting up a new hive and that Prajzner will again sedate and tag hundreds of bumblebees. That's something Gallagher said he's glad to miss.